The Vistide treatment for Relapsing Cytomegalovirus Retinitis in patients with AIDS is a research study designed to: 1) make intravenous Vistide more broadly available to patients with CMV retinitis who cannot tolerate, or have progressed despite treatment with Ganciclovir and/or foscarnet, and 2) gather additional information about the safety and effectiveness of intravenous Vistide in the treatment of relapsing CMV retinitis in patients with AIDS. Patients with AIDS are at high risk for reactivation of CMV. CMV infection may be asymptomatic. However, CMV may progress and cause severe and potentially disabling damage to the lungs, gastrointestinal tract and the retina of the eye.